Water tree growth in very low density polyethylene

The electrical and mechanical properties of a very low density polyetheylene (VLDPE) cross-linked using a suitable peroxide have been studied. Water tree growth in this cross-linked polyethylene (XLPE) was investigated under accelerated conditions. These experiments demonstrated an increased resistance of this compound to water tree growth depending strongly on the molding procedures. The results have been compared to those for a non-tree-retardant and a tree-retardant XLPE. The fusion, crystallization and annealing behavior of crosslinked VLDPE were studied also, by differential scanning calorimetry. The results can be explained either by the existence of a range of intermolecular structures or by the presence of easily crystallizable structures with greater steric hindrance than in conventional XLPE. There was no experimental evidence of phase separation of gel and sol from the melt. Rheology and cross-linkability of VLDPE indicated the suitability of this type of compound for cable extrusion